This high voltage power supply is useful for demonstration od the arcs and Jacob Ladder. With the current limitation ballasts you can operate the circuit about 1-2 minutes. Limiting inductors are made of unneeded ballasts for 150W sodium lamps. They have a U-shaped core part removed, is left only winding on T-shaped core part. This reduces the inductance to about 36mH. The entire high voltage power supply draws about 3.5 A from mains when open, 17.5 A short-circuit. Output short circuit current is 0.9 A, Open circuit voltage is 4200V. This supply could be connected without chokes, but the current in the circuit would be about 2.2 A, and the curent drawn from the mains about 45A. This makes MOTs hot very quickly and circuit breaker can trip, so I recommend using the current limiting inductors.